Ubiquity of Amino Accelerators and Antioxidants in Road Dust from Multiple Land Types: Targeted and Nontargeted Analysis

Abstract

Amino accelerators and antioxidants (AAL/Os), as well as their degradation derivatives, are industrial additives of emerging concern due to their massive production and use (particularly in rubber tires), pervasiveness in the environment, and documented adverse effects. This study delineated their interregional variations in road dust collected from urban/suburb, agricultural, and forest areas, and screened for less-studied AAL/O analogues with high-resolution mass spectrometry. 1,3-Diphenylguanidine (DPG; median concentration: 121 ng/g) and N-(1,3dimethylbutyl)-N′-phenyl-p-phenylenediamine quinone (6PPD-Q; 9.75 ng/g) are the most abundant congeners, constituting 69.7% and 41.4% of the total concentrations of AAL/Os (192 ng/g) and those of AAO transformation products (22.3 ng/g), respectively. The spatial distribution across the studied sites suggests evident human impacts, reflected by the pronounced urban signature and vehicle-originated pollution. Our nontargeted analysis of the most-contaminated road dust identified 16 AAL/O-related chemicals, many of which have received little investigation. Particularly, environmental and toxicological information remains extremely scarce for five out of the 10 most concerning compounds prioritized in terms of their dusty residues and toxicity including 1,2-diphenyl-3cyclohexylguanidine (DPCG), N, N′′-bis[2-(propan-2-yl)phenyl]guanidine (BPPG), and N-(4-anilinophenyl)formamide (PPD-CHO). Additionally, dicyclohexylamine (DChA), broadly applied as an antioxidant in automobile products, had an even greater median level than DPG. Therefore, future research on their health risks and (eco)toxic potential is of high importance.

Occurrence of Multiple Classes of Emerging Synthetic Antioxidants, Including p-Phenylenediamines, Diphenylamines, Naphthylamines, Macromolecular Hindered Phenols, and Organophosphites, in Human Milk: Implications for Infant Exposure

“…AAs are generally subdivided into p -phenylenediamines (PPDs), diphenylamines (DPAs), and naphthylamines (NPAs) . Recently, a ubiquitous quinone derivative of the tire rubber antioxidant N -(1,3-dimethylbutyl)- N ′-phenyl-PPD (6PPD), called 6PPD-quinone (6PPD-Q), has been identified as the crucial toxicant responsible for acute mortality in Coho salmon, making PPDs and PPD-derived quinones (PPD-Qs) attract worldwide attention. − Under this background, other AAs, including DPAs and NPAs, have been also brought into the purview of environmental research by our group and other groups. ,, To date, AAs, especially PPDs, have been widely detected in various environmental media and biota. ,− Although toxicological information on AAs remains quite limited, available studies have shown that DPAs possess high bioaccumulation potentials and can induce damage to the liver, spleen, and kidney of mammals. − Additionally, PPDs and NPAs can pose risks to aquatic organisms − and hepatotoxicity and developmental toxicity to mammals. , Currently, human exposure to AAs remains under-researched. Only a few recent studies confirmed the presence of 6PPD and/or 6PPD-Q in human urine, serum, and cerebrospinal fluid. − Given their environmentally widespread occurrence and toxic effects, human biomonitoring of AAs is urgently needed.…”

Comprehensive Identification and Ubiquitous Occurrence of Eight Classes of Rubber-Derived Vulcanization Accelerators in Urban Dusts

“…Among the eight classes of VAs, thiazoles and guanidines are becoming increasingly known to the public and raising growing environmental and health concerns. Global reports now document the widespread presence of thiazoles and guanidines, represented by MBT and DPG, in dust, soil, water, and human samples. − Furthermore, while most VAs are considered to be toxic, exact toxicity data remain limited or unavailable for these emerging substances. , VAs have been reported as the most frequent cause of allergic contact dermatitis resulting from the frequent use of rubber products such as latex gloves. − Existing data have indicated that human exposure to rubber VAs may pose a significant risk of developing cancers. , A compelling example is MBT, which, according to reports conducted by the International Agency for Research on Cancer, is likely carcinogenic to humans and has been associated with an increased incidence of urinary bladder cancer . Additionally, many VAs may exhibit multiple toxic effects based on toxicological prediction.…”

“…Representative VAs, including N -tert-butyl-2-benzothiazolesulfenamide (TBBS), N -cyclohexyl-2-benzothiazolesulfenamide (CBS), 2,2′-dithiobisbenzothiazole (MBTS), 2-mercaptobenzothiazole (MBT), and 1,3-diphenylguanidine (DPG), each with annual productions ranging 10,000 to 100,000 tons, , have become notable players. Despite increasing concerns regarding environmental pollution and safety associated with tire wear particles and tire rubber-derived antioxidants, such as N -(1,3-dimethylbutyl)- N ′-phenyl- p -phenylenediamine (6PPD), , attention toward the environmental impact of rubber-derived VAs remains largely inadequate, except for a few thiazoles (e.g., MBT) − and guanidines (e.g., DPG). − …”

Synthetic Antioxidants as Contaminants of Emerging Concern in Indoor Environments: Knowns and Unknowns

“…37 The occurrence of transformation products of synthetic antioxidants has also been delineated in sludge, road dust, or fishes. 18,38,39 Exposure to synthetic antioxidants is of particular concern because these chemicals can potentially pose health risks. For example, endocrine-disrupting effects and genotoxicity have been reported for 3-tert-butyl-4-hydroxyanisole (BHA), a commonly used SPA.…”

“…Synthetic antioxidants have also been detected in river water, sediment, sewage sludge, soil, outdoor air particulates, and biotas. ,,,− In addition to their presence in the environment, synthetic antioxidants have also been detected in human fingernails, serum, , urine, − follicular fluid, and breast milk . The occurrence of transformation products of synthetic antioxidants has also been delineated in sludge, road dust, or fishes. ,, …”